1. Field of the Invention
This invention relates to an ink-jet recording medium and, more particularly, it relates to an ink-jet recording medium to be used in applications where a transparent film layer is formed to cover the ink-receiving layer thereof after forming an image thereon.
2. Related Background Art
Various types of recording medium to be used for forming images by ink-jet printing are known to date. Besides, recording devices (printers) using an ink-jet printing technique have developed a wide variety of applications including electronic image information outputs of computers and communication networks and those of digital cameras, digital videos and scanners, which in turn urge the development of functionally improved recording devices. As a result, there is a demand for ink-jet recording medium having various sophisticated functional features that can accommodate the functional improvements of the recording device.
For instance, there is known a technique for improving the image quality by forming a laminate comprising an ink-receiving layer and a transparent film layer formed on the ink-receiving layer for the purpose of improving the glossiness and smoothness of the surface of the formed image as well as the maximum density of the image in order to achieve image quality comparable to that of silver salt photography and multi-color printing. The lamination process is utilized for improving not only the image quality but also the light fastness, the water fastness and the ozone fastness of the formed image to maintain high image quality for a prolonged period of time.
With a known technique that can be used for the lamination process, a transparent film layer with which a heat resistant substrate is coated is heated from the side of the heat resistant substrate so as to be transferred onto the ink-receiving layer of a recording medium and subsequently the heat resistant substrate is peeled off.
When the binder of the ink-receiving layer contains polyvinyl alcohol as a principle ingredient and the lamination process is conducted immediately after an ink-jet printing operation, a swell can appear between the substrate of the ink-jet recording medium and the ink-receiving layer form thereon while the substrate is heated. Additionally, when the heat resistant substrate is peeled off after the transfer of the transparent film layer, the ink-receiving layer can also be peeled off together with the heat resistant substrate. Therefore, there is a demand for a lamination process that is free from the above identified problems.
In view of the above described circumstances, it is therefore an object of the present invention to provide an ink-jet recording medium suitable for easy and excellent laminate formation and free from the problems such as swell arising between the ink-receiving layer and the substrate of the ink-jet recording medium immediately after an ink-jet printing operation, and peeling off of the ink-receiving layer at the time of peeling off a heat resistant substrate after the transfer of a transparent film layer. More specifically, an object of the present invention is to provide an ink-jet recording medium having a novel ink-receiving layer to which a transparent film layer is transferred in the lamination process without any problem.
As a result of the intensive research efforts for solving the above identified problems, the inventors of the present invention found that the tight contact between the ink-receiving layer and the substrate of the ink-jet recording medium is maintained and swells between them are prevented, when polyvinyl alcohol is used as a principal ingredient of a binder for fixing inorganic particles that are used to improve ink absorptivity, and the polyvinyl alcohol molecules are cross-linked by the heat-induced action of a cross-linking agent contained therein during the process of transferring the transparent film layer onto the ink-receiving layer after the ink-jet printing operation. The inventors of the present invention also found that both the phenomenon of swell arising between the substrate of the ink-jet recording medium and the ink-receiving layer and that of peeled-off of the ink-receiving layer arising in the operation of peeling off the heat resistant substrate that carries the transparent film layer on the surface thereof are eliminated by the use of such a binder.
Thus, according to the invention, there is provided an ink-jet recording medium for use in an ink-jet image forming method in which a transparent film layer formed on a substrate as coating is placed on an ink-receiving layer of the recording medium, and then the side of the substrate is heated to transfer the transparent film layer on the ink-receiving layer, followed by peeling off the substrate to laminate the transparent film layer on the surface of the ink-receiving layer, the ink-receiving layer containing polyvinyl alcohol and a cross-linking agent.
In another aspect of the invention, there is also provided an ink-jet printed article comprising the ink-jet recording medium according to the invention having an image formed on the ink-receiving layer thereof, the transparent film layer being formed on the ink-receiving layer as coating.
In still another aspect of the invention, there is also provided an image forming method comprising the steps of forming an image on the ink-receiving layer of the ink-jet recording medium by ink-jet and coating the ink-receiving layer with the transparent film layer by heating.
When an ink-jet recording medium according to the invention is subjected to a lamination process by heating and transferring the transparent film layer on the surface of the ink-receiving layer containing the above ingredients after an ink-jet printing operation, the obtained printed article maintains a high image quality particularly in terms of the glossiness and smoothness of the image surface and the image density as well as the fastness including the light fastness, the water fastness and the ozone fastness. Additionally, no problem occurs if the lamination process of heating and transferring the transparent film layer is conducted immediately after the ink-jet printing operation, so that an ink-jet recording medium according to the invention can reduce the time required for the entire process from the ink-jet printing operation to the completion of the lamination process. Therefore, an ink-jet printing process using an ink-jet recording medium according to the invention can enjoy a high printing speed.